The present disclosure generally relates to semiconductor devices, and particularly to semiconductor structures having a dielectric metal oxide spacer configured to enable a self-aligned contact, and methods of manufacturing the same.
Self-aligned contact structures employ a dielectric spacer around a gate stack, which is sufficiently resistant to etch chemistry employed to form a via hole extending to a surface located below the topmost surface of the gate stack. The material employed for the dielectric spacer has to be different from the dielectric material layer through which the via hole is formed. However, etch chemistries do not provide infinite selectivity. Thus, erosion of some portion of the dielectric spacer is inevitable if any surface of the dielectric spacer is exposed during the formation of the via hole in the dielectric material layer.
A successful implementation of a self-aligned contact scheme depends on providing sufficient selectivity in the etch process employed to etch the dielectric material layer relative to the material of the dielectric spacer. Typically, doped or undoped silicate glass or organosilicate glass is employed for the dielectric material layer, and silicon nitride is employed for the dielectric spacer. The selectivity of the currently available etch processes is not sufficient to maintain the undesirable etching to the dielectric spacer at an insignificant level. An excessive erosion of the dielectric spacer during formation of a self-aligned via hole can expose a conductive material within a gate stack to cause a direct electrical short, or can form a thin region in the eroded dielectric spacer that provides a leakage current path between a conductive material within a gate stack and a contact via through the thin region. Thus, without a reliable process that minimizes thinning of the dielectric spacer during a self-aligned via hole etch, a self-aligned contact scheme is prone to manufacturing a high percentage of defective devices that do not function or does not meet the specification from the beginning or unreliable devices that fail in time after some usage.